JPS6144573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hemming method for edge bending a workpiece (mainly sheet metal).

Conventional hemming processing is performed as shown in Fig. 1 A, B, and C.

That is, as a first step, the edge 1a of the workpiece 1 is bent by 90 degrees using a press or the like, as shown in FIG. The hemming process is completed by performing preliminary bending with the preliminary bending blade 2 as shown in FIG.

As described above, in the past, after the edge 1a of the workpiece 1 was bent at 90 degrees in the first step, two further steps were required: preliminary bending and final bending.

Conventionally, a device has been provided that performs the preliminary bending and main bending in conjunction with each other, but the structure of the device is complicated, and in particular, it is difficult to simultaneously hem two, three, or more sides of the workpiece. In this case, when the structure becomes more complicated and there are three or more sides, simultaneous processing is almost impossible.

In view of the above points, the present invention provides a method that eliminates the need for a pre-bending blade that performs pre-bending and allows the hemming process to be completed with a single bending blade.
The details of this invention will be explained below with reference to the drawings.

First, as shown in FIG. 2, the principle of the present invention is to form an inclined surface 10a having an angle .theta..degree. on the bending blade 10, thereby pressing the hem flange portion 11a of the workpiece 11.

In this case, the bending edge 10 of the component force P ₁ in the bending direction and the component force P ₂ in the compression direction generated on the hem flange portion 11a
The relationship with respect to the inclined surface 10a is tanθ=P ₁ /P ₂ (1).

Now, when trying to bend the hem flange part 11a in the _P1 direction in FIG. 2, if the resistance force at the contact point Q between the bending blade 10 and the hem flange part 11a is smaller than the component force _P1 in the bending direction, 11a slides in the direction _P1 along the inclined surface 10a of the bending blade 10, and can bend the hem flange 11a without buckling.

Here, the above resistance force can be expressed as P ₂ μ/cos (2). However, μ is the coefficient of friction on the inclined surface 10a of the bending blade 10.

Therefore, in order to bend the hem flange portion 11a without buckling, it is sufficient that the above equation (2) is smaller than P ₁ , so P ₂ μ/cos θ≦P ₁ ...(3) Above (1) (2) ) By substituting the result of equation (3) into equation (3), μ≦sinθtanθ ……(4) is obtained.

From equation (4) above, by reducing μ, θ
will also become smaller.

The above μ is about 0.04 even if the inclined surface 10a of the bending blade 10 is finished to a mirror surface, and is generally about 0.2 to 0.4.

When μ=0.04, θ≒2°30′ When μ=0.2, θ≒11°30′ When μ=0.3, θ≒18°00′ When μ=0.4, θ≒23°00′ On the other hand, hemming The purpose of processing is to bring the hem flange portion 11a into close contact with the hem surface 11b of the workpiece 11, so if the hem surface 11b is made horizontal and the bending blade 10 is made into the inclined surface 10a as shown in FIG. The hem flange portion 11a cannot be brought into close contact with the hem surface 11b.

Therefore, as shown in FIG. 3, the hem surface 11b of the workpiece 11 is inclined by the same angle θ as the inclined surface 10a of the bending blade 10, and the stopper surface 12 is also formed as an inclined surface 12a. The hemming process can be completed by bringing the hem flange portion 11a into close contact with the hem surface 11b.

This is the principle of the invention.

In general, the hem flange portion 1 of the workpiece 11
When bending 1a first, if it is bent vertically using a press or the like, it will not become vertical after the bending process, and will spring back and the angle with the hem surface 11b will be slightly (approximately 3 degrees). growing.

As a result, the contact angle of the bending blade 10 with the inclined surface 10a also changes.
Hem flange portion 11a of the workpiece 11 on side a
Increase the angle of initial contact with the object.

That is, as shown in FIG. 4, the angle of inclination α at the first contact point A between the inclined surface 10a of the bending blade 10 and the hem flange portion 11a of the workpiece 11 is set to be large.
(For example, at about 50 degrees with respect to the horizontal plane.) Further, even after hemming is completed, tight contact may not be achieved due to spring back of the hem flange portion 11a.

In order to prevent this, the bending starting point B of the hem flange portion 11a may be pressed more than the bottom portion.

Therefore, the inclination angle β at the position where the bending blade 10 contacts the bending starting point B of the hem flange portion 11a at the time of completion of hemming is made large as shown in FIG. If this is done, point B of the hem flange portion 11a will be pressed more than other portions when hemming by the bending blade 10 is completed.

Inclination angle α at point A and point B of the bending blade 10,
Theoretically, β may be set to an independent and distinct angle, and there is no problem even if it is given as one inclination angle extending from the inclination angle at point A to point B.

However, when considering the manufacturability of the bending blade 10,
It is preferable to provide these as one circular arc C, and in this case, the sliding movement of the hem flange portion 11a to the bending blade 10 can be made smoother.

The above-mentioned circular arc C needs to satisfy the above-mentioned conditions, and in order to do so, its center of curvature O passes through point B and the inclined surface 1 of the bending blade 10, as shown in FIG.
It is sufficient if it is located inside a perpendicular line perpendicular to 0a.

As explained above, the present invention has a surface in contact with the hem flange of the workpiece, when the friction coefficient of the surface is μ with respect to the horizontal surface, μ≦sinθtanθ
a single bending blade with an inclined surface having an angle θ, and a stopper surface with an inclined surface parallel to the inclined surface of the bending blade and on which the hem surface of the workpiece is placed in correspondence with the bending blade. In addition, the hem surface of the workpiece to be placed on the stopper surface is parallel to the stopper surface, and the hem flange portion is erected at an angle of [90°-θ] from the hem surface. Then, the single bending blade and the stopper surface are moved in a straight line parallel to the upright direction of the hem flange of the workpiece to bend and bring the hem flange into close contact with the hem surface. Completely eliminates the need for blades, simplifies the mold structure, increases processing speed,
The process can be shortened, multiple sides can be processed simultaneously, and production costs can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the conventional hemming procedure (A, B, C), Fig. 2 is an explanatory diagram of the principle of the present invention, and Fig. 3 is an explanatory diagram of the hemming method of the present invention based on the above principle. , FIG. 4 and FIG. 5 are explanatory diagrams of countermeasures against spring back of the hem flange portion, and FIG. 6 is an explanatory diagram showing a specific example of a preferable hemming die based on the present invention. 10...bending blade, 10a...slanted surface, 11...
Workpiece, 11a... Hem flange portion, 11b...
...Hem side, 12...Stopper side.

Claims (1)

[Claims] 1. The surface that comes into contact with the hem flange of the workpiece is
When the coefficient of friction of the surface is μ with respect to a horizontal surface, a single bending blade is formed as an inclined surface at an angle θ such that μ≦sinθtanθ, and the slope is parallel to the slope of the above-mentioned bending blade. It uses a stopper surface on which the hem surface of the workpiece is placed in correspondence with the bending blade, and
The hem surface of the workpiece to be placed on the stopper surface is parallel to the stopper surface, and the hem flange is erected at an angle of [90°-θ] from the hem surface. A hemming method characterized in that the bending blade and the stopper surface are moved in a straight line parallel to the upright direction of the hem flange of the workpiece to bend and bring the hem flange into close contact with the hem surface.